J Burke wrote:
> You can kinda-sorta turn non-high vowels into glides, but
> they're not very distinct from w or y (or j), and easily
> become those. Non-high glides do not exist as discrete
> segments in any natural language that I'm aware of.
IIRC I've seen transcriptions of Thai that have V+schwa diphthongs, but I think systematically they should be called V+[1]-glide (barred i) which is +high (and maybe even glide-[1] + V but I'm not sure).
>
> --- On Wed, 4/8/09, Edgard Bikelis
> <[log in to unmask]> wrote:
> Indeed, but why does [i u] have a
> > respective glide, and, say, [a] does not?
> >
> > [ei] ~ [ej]
> > [eu] ~ [ew]
> > [ea] ~ ?
> >
The off-glide equivalent of [a] would probably be schwa or [1]. I think it's possible to have diphthongs with a central (high [1] or mid [@]) off-glide (there may however be intervening glides in e.g. [i(j)@] or [u(w)@] etc.
> >
> > >
As I understood Linvi Charles' original question, he was also wondering why rising diphthongs (glide to main vowel) are relatively rare. They do exist in Spanish (puerto [pwErto] piensa [pjensa], but it may be a matter of analysis. (Is Span ya considered a diphthong or CV? I think CV.) In Engl. we tend to think of [w,j] in these cases as consonants/clusters. "yet, wet" [yEt, wEt] are considered /CVC/, twelve, twirl etc are considered C-clusters. CjV- IIRC is very rare in Engl (all loanwords like piano), though "long u" [juw] may qualify as our only triphthong,